Drillers contracted by mining companies are required to drill numbers of exploratory subsurface drill holes at a chosen mine site to extract underground core samples in order to determine locations of mineralisation and the feasibility to proceed with mineral extraction.
Such operations extract a core during drilling (in ‘diamond drill-bit drilling’ the bit has a centre hole which allows the core sample to enter through during drilling). Core lengths are variable, but usually between 3 m and 6 m lengths and are extracted progressively for the entire hole.
Each extracted core sample is marked for its orientation position before extraction, with additional survey data of that cores position such as azimuth (angle of North-South deviation), dip angle, depth the core was extracted from and other additional data to verify data correctness. Financial costs associated with such operations are based on distance (meters) drilled, number of holes, sub-surface targets reached and number of targets concluded.
Drill-Rig Activity:
1) Equipment Needed to Achieve the Above Basic Requirements
Inventory of instrumentation and ancillary equipment required to carry out drilling activity such as surveying and core orientation. These pieces of equipment and sub-assemblies have to be possibly transported to remote locations by air cargo, helicopter or by road. In remote areas suitable for mining and drilling operations, such roads are often unsealed and within harsh environmental conditions.
2) Extracting Core Samples During Drilling
a) A core-orientation unit is attached to a ‘back-end assembly’, which is inserted into a drill hole during drilling and is brought to the surface when the core sample is extracted with the core orientation unit.
b) The core orientation unit needs to be removed (unscrewed) from the back-end assembly to begin the process of orienting the extracted core. The core is removed after orientation marking, and then the core orientation unit is re-installed to the back-end assembly before inserting into the drill hole for the next core sample extraction. This process is time consuming and costly considering the high cost of the drill rig on-site and that this process is repeated every 3 or 6 meters of drilling. Drilling depths are usually between 500 meters and 2 km, with deeper drilling expected in the future. To speed up the process, a pair of core orientation units are used on two identical assemblies and alternated when drilling for core samples, however the operator still needs to go through the motion of removing and re-installing the core orientation unit for every sample retrieved.
c) As drilling depths increases, the drill bit size is reduced to cope with the deeper hole drilling, as a consequence, a smaller size diameter core orientation unit is required to follow the reduced hole size. As a norm, drillers need to have three sizes of core orientation units, two of each size, making a total of six core orientation units. These units are usually made of heavy thick walled stainless steel to withstand high pressures during deep hole drilling. This adds substantial weight to the core orientation equipment inventory.
3) Surveying the Drill Hole at Different Depths
a) In order to identify the exact underground locations of each extracted core sample, a number of surveys of the drill hole need to be carried out in between the drilling and core extraction process. A survey instrument is used in the drill hole to measure azimuth, hole inclination (or dip), and other data. As a minimum, hole surveys need to be taken every 30 meters of drilling. The hole path/trajectory is then extrapolated mathematically and the extracted 6m core samples positioning is then calculated from the plotted path.
b) The process of surveying a drill hole at a determined depth involves inserting a ‘Survey instrument probe’ into a pressure protected brass barrel, attaching the probe pressure barrel to three lengths of 1.2 m aluminium rod extensions (to avoid anomalous magnetic readings when the probe is in close proximity to the drill bit and steel drill pipe extensions), attaching the entire length to a back-end assembly, which is then inserted into the end of the drilled hole and through the hollowed centre of the circular drill bit. With the drill bit and steel piping pulled back past the survey probe and the three rod extensions, a survey reading can then be recorded at the last drilled position of the drill hole. This total assembly including the survey probe, its brass pressure barrel and three aluminium extension rods again adds substantial weight and considerable assembly/disassembly time to the survey process.
c) On retrieving the probe assembly, the probe needs to be removed from the brass pressure barrel in order to retrieve the recorded survey readings from the drill hole. This can be a lengthy process with added care required not to damage the instrument during handling or being dropped in water or mud as would normally be the condition at a drill-rig site.
4) Maintaining a Progressive Drilling Log
a) A mandatory requirement for all drilling activity is to record events, activities, instrument data and progress/achievement of underground targets. Traditionally (and still used in many drill rigs globally), the method of recording and logging of drilling activity is carried out painstakingly using manual pen and paper recording methods.
b) The pieces of paper are compiled and manually checked for errors or omissions, corrected after discussions with drill rig operators and on-site geologists, and then sent to the drilling companies' administrative office for manual transfer of data from the ‘progressive log of drilling’ sheets to computer terminals.
c) To accommodate for multiple site log data entry, there is usually a pool of typists performing the data entry task. Having to re-enter data in this manner can sometimes cause data errors which would then have to be re-checked and corrected as necessary. There is also the need to interpret the handwritten sheets to ensure data is recorded in the required format so it can be used by 3rd party software programs which eventually provide billing to the mining companies that contract the drilling companies.
d) If sufficient detailed information can be recorded on the progressive log of drilling sheet process, the drilling company has the added advantage of extracting metrics from the recorded data that can provide a thorough analysis of drill-rig costs (labour and consumables), efficiencies, safety issues etc. This additional data is not always available due to insufficient data recording at the drill rigs because of inaccessibility of the data or time constraints when drilling towards underground targets within a limited time. Summary of current operational methods used for basic activities at drill-rig sites to orient core samples, measure survey data and record all activity at the drill rig site.
To accomplish the above, drill-rig operators use core orientation tools, survey probes and a number of manual pen and paper recording means to log drilling activity and events. Core orientation and Survey tools are available from a number of different international suppliers and attempts have been made to electronically record/log rig activity using ‘Tough-books’ and other commercially available laptops and hand-held computers. The problems experienced from present operating methods comes from having to manually record data from the variety down-hole instruments source from various 3rd party suppliers, which may or may not have compatible formats, then transferring the data to the overall manual logging sheets or laptop as required for eventual recording and billing to customer.
This current method is prone to human error, possible data incompatibility and excessive time required to compile information which would require further re-compilation at head office to include other neighbouring drill-rig data and activity/events. Time delays and inherent inaccuracies as a result of manual human data recording can cause delays in invoicing and receiving payment, and at worst, not charging for all items due to missing or poor recording methods.
A further inconvenience to the driller is the need to keep an inventory of third party core orientation/survey instruments, different manufacturer spare parts and related consumables such as batteries, long and cumbersome brass pressure barrels to protect survey instruments, sealing/waterproofing ‘O’ rings and grease to install associated pressure barrel housings before using the survey probes. Apart from having to take stock of a large, and separately cased (if at all) collection of instruments with associated hardware and consumables, the operator has to gain familiarity with each instrument's method of operation and be able to manually record and integrate the various data formats and results into a common ‘paper form’ which can be later manually keyed in for geologist use or accounting purposes.
The present invention seeks to alleviate or overcome one or more of the aforementioned problems.
With this in mind, it is desirable of one or more forms of the present invention to provide a system or method that utilises a reduced number of components compared with standard systems and which enables common communication between various components.
It is further desirable of one or more embodiments of the present invention to make use of electronic hardware and software to reduce time and cost, with a reduction in overall equipment count and weight and the capability to simplify and streamline instrumentation and operator procedures.